Great circle routes or great circle mapping is the process of navigating a ship or aircraft along the route of a great circle. A great circle track is the shortest distance between two points on the surface of the earth. The earth is not exactly spherical, but the formulas for a sphere are accurate enough to calculate the shortest distance between two points. It is important to note that the great circle is measured along the surface of the sphere, not as a straight line through the sphere's interior.
